This invention relates to silicone foam control compositions. More particularly, this invention relates to silicone foam control compositions comprising a silicone antifoam agent, mineral oil, a polydiorganosiloxane containing at least one polyoxyalkylene group, and a finely divided filler.
The use of various silicone containing compositions as antifoams or defoamers is known. In this regard, it is well established that this art is highly unpredictable and slight modification can greatly alter performance of such compositions. Most of these compositions contain silicone fluid (usually dimethylpolysiloxane), often in combination with small amounts of silica filler. Additionally, these compositions may include various surfactants and dispersing agents in order to impart improved foam control or stability properties to the compositions.
Silicone compositions which are useful as foam control agents have been taught in the art. For example, Aizawa et al., in U.S. Pat. Nos. 4,639,489 and 4,749,740, the disclosures of which are hereby incorporated by reference, teach a method for producing a silicone defoamer composition wherein a complex mixture of polyorganosiloxanes, filler, a resinous siloxane and a catalyst to promote reaction of the other components are heated together at 50xc2x0 C. to 300xc2x0 C.
More recently, a method for preparing a composition similar to that described by Aizawa et al., cited supra, was disclosed by Miura in U.S. Pat. No. 5,283,004, the disclosure of which is hereby incorporated by reference. In this disclosure, the above mentioned complex silicone mixture additionally contains at least 0.2 weight parts of an organic compound having at least one group selected from xe2x80x94COR, xe2x80x94COORxe2x80x2 or xe2x80x94(ORxe2x80x3)nxe2x80x94, wherein R and Rxe2x80x2 are hydrogen or a monovalent hydrocarbon group, Rxe2x80x3 is a divalent hydrocarbon group having 2 to 6 carbon atoms and the average value of n is greater than one. It is further disclosed that all the ingredients, including a catalyst, must be reacted at elevated temperatures to obtain the desired antifoam agent.
John et al., in European Patent Application No. 217,501, published Apr. 8, 1987, discloses a foam control composition which gives improved performance in high foaming detergent compositions which comprises (A) a liquid siloxane having a viscosity at 25xc2x0 C. of at least 7xc3x9710xe2x88x923 m2/s and which was obtained by mixing and heating a triorganosiloxane-endblocked polydiorganosiloxane, a polydiorganosiloxane having at least one terminal silanol group and an organosiloxane resin, comprising monovalent and tetravalent siloxy units and having at least one silanol group per molecule, and (B) a finely divided filler having its surface made hydrophobic. John et al. further describes a method for making the foam control compositions and detergent compositions containing said foam control compositions.
McGee et al. in U.S. Pat. No. 5,380,464 discloses a foam control composition comprising a silicone defoamer reaction product and a silicone glycol copolymer which is particularly effective in defoaming highly acidic or highly basic aqueous systems. However, when a foam control composition comprising a silicone antifoam agent and a silicone glycol copolymer is employed, it is added in the form of a liquid or after dilution with water to a foamable liquid thus requiring higher levels of the silicone copolymer.
McGee et al. in U.S. Pat. No. 5,543,082 discloses a foam control composition prepared by mixing at room temperature a silicone defoamer reaction product, a silicone glycol copolymer, and a hydroxyl-endblocked polydiorganosiloxane polymer.
In European Patent Application No. 0638346 is disclosed a composition comprising a reaction product, a nonaqueous liquid continuous phase, and a moderately hydrophobic particulate stabilizing aid. EP""346 discloses that the reaction product is prepared by heating a mixture of a polyorganosiloxane fluid, a silicon compound, a finely divided filler, and a catalytic amount of a compound for promoting the reaction of the other components at a temperature of 50xc2x0 C. to 300xc2x0 C. EP""346 further discloses that these compositions can further contain at least one nonionic silicone surfactant, and a nonreinforcing inorganic filler.
In European Patent Application No. 0663225 is disclosed a foam control composition comprising a silicone antifoam agent and a crosslinked organopolysiloxane polymer having at least one polyoxyalkylene group.
Fey et al. in U.S. Pat. No. 5,908,891 discloses a dispersible silicone composition comprising (I) a silicone composition prepared by reacting a polyorganosiloxane, a silicon compound, optionally a finely divided filler, and a catalytic amount of a compound for promoting the reaction of the other components and (II) mineral oil. Fey et al. further discloses that the mineral oil is effective as a dispersing agent for the silicone composition (I).
This invention relates to silicone foam control compositions. More particularly, this invention relates to silicone foam control compositions comprising a silicone antifoam agent, mineral oil, a polydiorganosiloxane containing at least one polyoxyalkylene group, and a finely divided filler.
It is an object of the present invention to prepare silicone compositions which can be advantageously utilized to control foam in foam producing systems.
It is a further object of the present invention to provide silicone compositions wherein there is provided improvement in the control of foaming behavior.
It is a further object of the present invention to provide silicone foam control compositions which are stable and easily dispersible.
The present invention relates to a silicone foam control composition comprising (I) a silicone antifoam agent prepared by reacting at a temperature of 50xc2x0 C. to 300xc2x0 C. a mixture comprising: (i) 100 weight parts of at least one polyorganosiloxane selected from the group consisting of (A) a polyorganosiloxane having a viscosity of about 20 to 100,000 mm2/s at 25xc2x0 C. and being expressed by the general formula R1aSiO(4-a)/2 in which R1 is a monovalent hydrocarbon or halogenated hydrocarbon group having 1 to 10 carbon atoms and a has an average value of 1.9 to 2.2, (B) a polyorganosiloxane having a viscosity of 200 to about 100 million mm2/s at 25xc2x0 C. expressed by the general formula R2b(R3O)cSiO(4-b-c)/2 in which R2 is a monovalent hydrocarbon or halogenated hydrocarbon group having 1 to 10 carbon atoms, R3 is hydrogen or a monovalent hydrocarbon group having 1 to 10 carbon atoms, b has an average value of 1.9 to 2.2 and c has a sufficiently large value to give at least one xe2x80x94OR3 group in each molecule, at least one such xe2x80x94OR3 group being present at the end of the molecular chain, and (C) a mixture of (A) and (B); (ii) 0.5 to 20 weight parts of at least one silicon compound selected from (a) an organosilicon compound of the general formula R4dSiX4-d in which R4 is a monovalent hydrocarbon group having 1 to 5 carbon atoms, X is selected from a halogen atom or a hydrolyzable group and d has an average value of one or less, (b) a partially hydrolyzed condensate of said compound (a), (c) a siloxane resin comprising (CH3)3SiO1/2 units and SiO4/2 units wherein the ratio of (CH3)3SiO1/2 units to SiO4/2 units is 0.4:1 to 1.2:1, or (d) a condensate of said compound (c) with said compound (a) or (b); and (iii) a catalytic amount of a compound for promoting the reaction of components (i) and (ii); (II) at least one mineral oil; (III) at least one polydiorganosiloxane having at least one polyoxyalkylene group; and (IV) at least one finely divided filler. The silicone foam control compositions of this invention can optionally comprise a polyglycol.
The silicone foam control compositions of this invention comprise (I) a silicone antifoam agent, (II) at least one mineral oil, (III) at least one polydiorganosiloxane containing at least one polyoxyalkylene group, and (IV) at least one finely divided filler. Component (I) of the present invention can be prepared by reacting (i) a polyorganosiloxane, (ii) a silicon compound, and (iii) a catalytic amount of a compound for promoting the reaction of the other components.
Component (i) may be selected from (A) polyorganosiloxanes comprising siloxane units of the general formula R1aSiO(4-a)/2 and having a viscosity of 20 to 100,000 mm2/s (centistokes (cS)) at 25xc2x0 C. The organo groups R1 of the polyorganosiloxane (A) are the same or different monovalent hydrocarbon or halogenated hydrocarbon groups having one to ten carbon atoms. Specific examples thereof are well known in the silicone industry and include methyl, ethyl, propyl, butyl, octyl, trifluoropropyl, phenyl, 2-phenylethyl and vinyl groups. The methyl group is particularly preferred. In the above formula, a has a value of 1.9 to 2.2. It is particularly preferred that polyorganosiloxane (A) is a trimethylsilyl-terminated polydimethylsiloxane having a viscosity of about 350 to 15,000 mm2/s at 25xc2x0 C.
Alternatively, component (i) may be selected from (B) polyorganosiloxanes comprising siloxane units of the general formula R2b(R3O)cSiO(4-b-c)/2 and having a viscosity of 200 to 100 million centistokes at 25xc2x0 C. wherein R2 is independently selected from the monovalent hydrocarbon or halogenated hydrocarbon groups designated for group R1, R3 is a hydrogen atom or R2, and the xe2x80x94OR3 group is present at least at the end of a molecular chain of the polyorganosiloxane. The value of b is from 1.9 to 2.2 and c has a value so as to provide at least one xe2x80x94OR3 group per molecule. It is particularly preferred that polyorganosiloxane (B) is a hydroxyl-terminated polydimethylsiloxane having a viscosity of about 1,000 to 50,000 mm2/s at 25xc2x0 C. Component (i) may also be (C) a mixture of (A) and (B) in any proportion.
Component (ii) is at least one silicon compound selected from (a) to (d):(a) an organosilicon compound of the general formula R4dSiX4-d wherein R4 is a monovalent hydrocarbon group having one to five carbon atoms, X is a halogen atom or a hydrolyzable group, such as xe2x80x94OR5 or xe2x80x94OR6OR7, in which R6 is a divalent hydrocarbon group having one to five carbon atoms and R5 and R7 are each a hydrogen atom or a monovalent hydrocarbon group having one to five carbon atoms, the average value of d not exceeding 1, (b) a partially hydrolyzed condensate of the compound (a), (c) a siloxane resin comprising (CH3)3SiO1/2 and SiO2 units and having a (CH3)3SiO1/2/SiO2 ratio of 0.4/1 to 1.2/1, or (d) a condensate of the siloxane resin (c) with the compound (a) or (b). It is preferred that component (ii) is selected from either an alkyl polysilicate wherein the alkyl group has one to five carbon atoms, such as methyl polysilicate, ethyl polysilicate and propyl polysilicate, or the siloxane resin (c). Most preferably, component (ii) is either ethyl polysilicate or a siloxane resin copolymer comprising (CH3)3SiO1/2 units and SiO2 units in a molar ratio of approximately 0.4:1 to 1.2:1.
Component (iii) is a compound used as a catalyst for promoting the reaction of the other components. Any compound which promotes condensation reactions or rearrangement/condensation reactions is suitable as component (iii). It is preferably selected from siloxane equilibration catalysts, silanol-condensing catalysts, or a combination thereof. Catalysts suitable as component (iii) are exemplified by alkali metal hydroxides such as potassium hydroxide, sodium hydroxide, or cesium hydroxide, alkali metal silanolates such as potassium silanolate, alkali metal alkoxides such as potassium isopropoxide or potassium ethoxide, quaternary ammonium hydroxides such as betahydroxyethyltrimethyl ammonium hydroxide, benzyltrimethyl ammonium hydroxide; and tetramethyl ammonium hydroxide, quaternary ammonium silanolates, quaternary phosphonium hydroxides such as tetrabutyl phosphonium hydroxide and tetraethylphosphonium hydroxide, quaternary phosphonium silanolates, metal salts of organic acids such as dibutyltin dilaurate, stannous acetate, stannous octanoate, lead napthenate, zinc octanoate, iron 2-ethylhexoate, and cobalt naphthenate, mineral acids such as sulfuric or hydrochloric acid, organic acids such as acetic acid or organosulfonic acids, and ammonium compounds such as ammonium carbonate or ammonium hydroxide. It is preferred that the catalyst is selected from potassium silanolate, potassium hydroxide, or sodium hydroxide.
The mixture can further comprise up to 30 weight parts of component (iv) a finely divided filler. The finely divided filler is exemplified by fumed, precipitated, or plasmatic TiO2, Al2O3, Al2O3/SiO2, ZrO2/SiO2, and SiO2. The finely divided filler can hydrophilic or hydrophobic. The filler can be hydrophobed during manufacture (i.e. in-situ) or independently. Various grades of silica having a particle size of several millimicrons to several microns and a specific surface area of about 50 to 1000 m2/g, preferably a surface area of 50 to 300 m2/g, are commercially available and suitable for use as component (iv). Preferably component (iv) is a hydrophobic silica having a surface area of about 50 to 300 m2/g.
The mixture can further comprise up to 20 weight parts of component (v), a polyorganosiloxane comprising siloxane units of the general formula R8e(R9O)fSiO(4-e-f)/2 and having a viscosity of 5 to 200 mm2/s at 25xc2x0 C. wherein R8 is a monovalent hydrocarbon or halogenated hydrocarbon group having one to ten carbon atoms and R9 is hydrogen or a monovalent hydrocarbon group having one to ten carbon atoms. The value of e is between 1.9 and 2.2 and f has a value so as to provide two or more xe2x80x94OR9 groups in each molecule. It is particularly preferred that component (v) is a hydroxyl-terminated polydimethylsiloxane having a viscosity of about 10 to 100 mm2/s at 25xc2x0 C. It is preferred that component (v) is added when filler (iv) is a hydrophilic silica.
A mixture of components (i), (ii), and (iii), optionally containing components (iv) and/or (v), is reacted under heat to produce the silicone antifoam agent (I), the proportions of the various components being: Component (i)xe2x80x94100 weight parts; Component (ii) xe2x80x940.5 to 20, preferably 1 to 7, weight parts; Component (iii) xe2x80x94A catalytic amount (usually in the range of 0.03 to 1 part by weight); Component (iv), if present, xe2x80x94up to 30, preferably 1 to 15, and highly preferred is 5 to 15 weight parts; Component (v), if present, xe2x80x94up to 20, preferably 1 to 10, weight parts.
The proportions of components (A) and (B) used depends largely on their respective viscosities. It is preferable to use a mixture of (A) and (B) which has a viscosity of 1,000 to 100,000 mm2/s at 25xc2x0 C.
The silicone antifoam agent (I) is prepared by first mixing components (i), (ii), and (iii) and heating this blend to about 110 to 120xc2x0 C. Finely divided filler (iv), if desired, is then uniformly mixed in using an appropriate dispersing device, such as a homomixer, colloid mill or triple roll mill. The resulting mixture is heated at a temperature of 50xc2x0 C. to 300xc2x0 C., preferably 100xc2x0 C. to 300xc2x0 C., and reacted for one to eight hours, although the reaction time varies depending on the temperature. If component (v) is to be employed in the composition, it is generally added after the filler (iv). It is preferable to carry out all mixing and heating operations in an inert gas atmosphere in order to avoid any danger and to remove volatile matter (unreacted matter, by-products, etc.). The mixing order of the components and the heating temperature and time as hereinabove stated are not believed critical, but can be changed as required. It is further preferred that, after reaction, the catalyst is neutralized to further stabilize silicone antifoam agent (I).
Alternatively, silicone antifoam agent (I) preferably comprises a diorganopolysiloxane, a silicon compound, and a catalyst for promoting the reaction of these components, and this combination optionally containing a filler such as silica. These systems contain a mixture of a trimethylsilyl-terminated polydimethylsiloxane and a diorganopolysiloxane having silicon-bonded hydroxyl groups or silicon-bonded alkoxy groups along its main chain or at its chain ends, said alkoxy groups having from 1 to 6 carbon atoms. The silicon compound (ii) acts as a crosslinker for the diorganopolysiloxane by reacting with the functionality of the latter. It is further preferred that the above diorganopolysiloxane is either a linear or a branched polymer or copolymer of siloxane units selected from dimethylsiloxane units, methylphenylsiloxane units or methyltrifluoropropylsiloxane units. Most preferably, the diorganopolysiloxane of component (A) is a polydimethylsiloxane containing Si-bonded hydroxyl or methoxy functionality. The above mentioned silicon compound (ii) is preferably a siloxane resin comprising (CH3)3SiO/2 and SiO2 units and having a molar ratio of (CH3)3SiO1/2/SiO2 between 0.4:1 and 1.2:1. The latter resin may be prepared according to methods taught in, e.g., U.S. Pat. No. 2,676,182 to Daudt et al. and typically contains from about 0.5 to about 3 weight percent of hydroxyl groups.
A highly preferred silicone antifoam agent is a homogeneous blend of a hydroxyl- terminated polydimethylsiloxane, a trimethylsilyl- terminated polydimethylsiloxane having a viscosity in the range of about 1,000 to 50,000 mm2/s at 25xc2x0 C., an alkyl polysilicate wherein the alkyl group has one to five carbon atoms, such as methyl polysilicate, ethyl polysilicate and propyl polysilicate, and a potassium silanolate catalyst reacted at a temperature of 50 to 300xc2x0 C.
The silicone antifoam agent (I) can also be a silicone antifoam agent comprising (a) silicone and (b) silica and can be prepared by admixing a silicone fluid with a hydrophobic silica. In industrial practice, the term xe2x80x9csiliconexe2x80x9d has become a generic term which encompasses a variety of relatively high molecular weight polymers containing siloxane units and hydrocarbon groups of various types. Preferred as component (a) are polydimethylsiloxanes having a molecular weight within the range of from about 2,000 to about 200,000. Component (b) is exemplified by silica aerogels, xerogels, or hydrophobic silicas of various types. Any of several known methods may be used for making a hydrophobic silica which can be employed herein in combination with a silicone fluid as the antifoam agent. For example, a fumed silica can be reacted with a trialkyl chlorosilane (i.e. xe2x80x9csilanatedxe2x80x9d) to affix hydrophobic trialkylsilane groups on the surface of the silica. Silicas having organosilyl groups on the surface thereof are well known and can be prepared in many ways such as by contacting the surface of a fumed or precipitated silica or silica aerogel with reactive silanes such as chlorosilanes or alkoxysilanes or with silanols or siloxanols or by reacting the silica with silanes or siloxanes. Various grades of silica having a particle size of several millimicrons to several microns and a specific surface area of about 500 to 50 m2/g are commercially available and several hydrophobic silicas having different surface treatments are also commercially available.
Component (I) is present in the silicone foam control compositions of this invention in an amount from 10-80 weight parts, preferably from 30 to 60 weight parts, and most preferably from 40 to 60 weight parts, said weight parts being based on the total weight of the composition.
Component (II) is mineral oil. The term xe2x80x9cmineral oilxe2x80x9d as used herein refers to hydrocarbon oils derived from carbonaceous sources, such as petroleum, shale, and coal, and equivalents thereof. The mineral oil of component (II) can be any type of mineral oil, many of which are commercially available, including heavy white mineral oil which is high in paraffin content, light white mineral oil, petroleum oils such as aliphatic or wax-base oils, aromatic or asphalt-base oils, or mixed base oils, petroleum derived oils such as lubricants, engine oils, machine oils, or cutting oils, and medicinal oils such as refined paraffin oil. The above mentioned mineral oils are available commercially at a variety of viscosities from Amoco Chemical Company (Chicago, Ill.) under the tradename Amoco White Mineral Oil, from Exxon Company (Houston, Tex.) under the tradenames Bayol(trademark), Marcol(trademark), or Primol(trademark), from Lyondell Petrochemical Company (Houston, Tex.) under the trade name Duoprime(copyright) Oil, and from Shell Chemical Company (Houston, Tex.) under the tradename ShellFlex(copyright) Mineral Oil. Preferably the mineral oil has a viscosity of from about 1 to about 20 millipascal-seconds at 25xc2x0 C. Component (II) can also be a mixture of the above-described mineral oils.
Component (II) is present in the silicone foam control compositions of this invention in an amount from 10-80 weight parts, preferably from 30 to 60 weight parts, and most preferably from 30 to 50 weight parts, said weight parts being based on the total weight of the composition.
Component (III) is at least one polydiorganosiloxane compound having at least one polyoxyalkylene group. The polyoxyalkylene group is exemplified by polyoxyalkylene groups having the formulae
xe2x80x94R10(OCh2Ch2)gOR11,

wherein R10 is a divalent hydrocarbon group having from 1 to 20 carbon atoms, R11 is selected from a hydrogen atom, an alkyl group, an aryl group, or an acyl group, and g, h, and i independently have an average value from 1 to 150. As used herein to describe Component (III), the polydiorganosiloxane having at least one polyoxyalkylene group, it is understood that the various siloxane units and the oxyethylene, oxypropylene and oxybutylene units may be distributed randomly throughout their respective chains or in respective blocks of such units or in a combination of random or block distributions.
Those skilled in the art will appreciate that the term xe2x80x9cpolydiorganosiloxane having at least one polyoxyalkylene groupxe2x80x9d standing alone, encompasses a number of compounds, including those based upon cyclic and resinous siloxane compounds. While cyclic and resinous oxyalkylene-modified siloxanes can be used in the foam control compositions of this invention, they are comparatively expensive and thus, are not as cost effective as the linear polyoxyalkylene-containing polydiorganosiloxane compounds described hereinbelow.
Preferably Component (III) is a polydiorganosiloxane compound having the formula
Me3SiO(Me2SiO)x(MeQSiO)ySiMe3,
wherein Q is selected from the group consisting of

wherein Me denotes methyl, x has an average value from 100 to 500, y has an average value from 1 to 50, z has a value of 2 to 10, g has an average value of 1 to 36, and h has 25 an average value of 1 to 36.
Component (III) of the silicone foam control compositions of this invention can also be a cross-linked polydiorganosiloxane polymer having at least one polyoxyalkylene group. This class of compounds has been generally described by Bahr et.al. in U.S. Pat. Nos. 4,853,474 and 5,136,068, incorporated herein by reference to teach cross-linked polydiorganosiloxane polymers suitable as (III). Compounds suitable as (III) include polydiorganosiloxane-polyoxyalkylene polymer molecules which are intentionally cross-linked through a cross-linking agent joined thereto by nonhydrolyzable bonds and being free of internal hydrolyzable bonds.
These may be obtained by a method comprising preparing a cross-linked polydiorganosiloxane polymer and combining a polyoxyalkylene group therewith or by a method comprising preparing a linear polyorganosiloxane having a polyoxyalkylene group combined therewith and cross-linking the same.
The cross-linking in this system can be attained through a variety of mechanisms. Those skilled in the art will readily recognize the systems wherein the required components are mutually compatible to carry out the method of preparing these polydiorganosiloxanes. By way of illustration, an extensive bibliography of siloxane polymer chemistry is provided in Siloxane Polymers, S. J. clarson and J. A. Semlyen eds., PTR Prentice Hall, Englewood cliffs, N.J., (1993).
Not to be construed as limiting this invention, it is preferred that the cross-linking bonds and the bonds to the polydiorganosiloxane-polyoxyalkylene molecules are not hydrolyzable, and that the cross-linking bridge contains no hydrolyzable bonds. It is recognized that similar emulsifiers wherein the polyoxyalkylene units are attached to the organopolysiloxane units via SiOC bonds are useful in applications not requiring extended stability under conditions where hydrolysis may occur. It is further recognized that such emulsifiers containing cross-links formed by SiOC bonds offer benefits of improved emulsion stability and consistency in such applications not requiring extended stability under conditions where hydrolysis may occur.
Preferably, the cross-linked polydiorganosiloxane polymer is obtained by the addition reaction between the following components: (i) an organopolysiloxane having an Sixe2x80x94H group at each of its terminals and a polydiorganosiloxane having at least two allyl groups in the side chains of each molecules thereof, or (ii) more preferably, an polydiorganosiloxane having at least two Sixe2x80x94H groups in the side chains of each molecule thereof, and a polydiorganosiloxane having each of its terminals blocked with an allyl group or a silanol group.
The preferred cross-linking radical is a vinyl-terminated polydiorganosiloxane used in combination with an Sixe2x80x94H containing backbone. This organosiloxane bridge should not contain any reactive sites for the polyoxyalkylene moieties. An organosiloxane bridge cooperates with the siloxane backbones which it bridges to create a siloxane network at the interface of water and the silicone antifoarn agent. This network is thought to be important in effecting the stabilizing properties and characteristics of the present invention. The siloxane bridge works with other types of antifoams. Other bridge types may be more suitable for non-silicone antifoams (e.g. an alkane bridge for mineral oil based antifoams).
The cross-linked polydiorganosiloxane polymer to be used as (III) should be one that satisfies the following conditions: (1) it has a three-dimensional crosslinked structure, (2) it has at least one polyoxyalkylene group, and (3) it has fluidity (i.e. it is xe2x80x9cfree flowingxe2x80x9d). The term xe2x80x9cthree-dimensional cross-linked structurexe2x80x9d used herein denotes a structure in which at least two organopolysiloxane molecules are bonded together through at least one bridge.
The exact number of polydiorganosiloxane-polyoxyalkylene polymer molecules which will be bridged together will vary within each compound. One limitation on such cross-linking is that the overall molecular weight must not become so great as to cause the material to gel. The extent of cross-linking must thus also be regulated relative to the molecular weight of each individual polymer molecule being cross-linked since the overall molecular weight must also be maintained sufficiently low to avoid gelling. In controlling the cross-linking reaction there is also the possibility that some un-cross linked material will be present.
In the present invention, it is preferred that component (III) is a compound having a viscosity of 100 to 100,000 mm2/s at 25xc2x0 C. and having the unit formula: 
wherein R12 is a monovalent hydrocarbon group, A is a group having the formula (Ch2)qxe2x80x94(R142SiO)rSi(Ch2)s or the formula O(R142SiO)rxe2x80x94SiO wherein R14 denotes a monovalent hydrocarbon group, q has a value of 2 to 10, r has a value of 1 to 5000, s has a value of 2 to 10, R13 denotes a group having its formula selected from the group consisting of: 
wherein R15 is selected from a hydrogen atom, an alkyl group, an aryl group, or an acyl group, t has a value of 2 to 10, u has a value of from greater than zero to 150, v has a value of from greater than zero to 150, and w has a value of from greater than zero to 150, j has a value of 1 to 1000, k has a value of from greater than zero to 30, 1 has a value of 1 to 1000, m has a value of 1 to 1000, n has a value of from greater than zero to 30, p has a value of 1 to 1000. The groups R12 and R14 can be the same or different as desired and are preferably alkyl groups or aryl groups and it is highly preferred that they are both methyl.
In the formulae hereinabove, it is preferred that j has a value of 1 to 500 and it is highly preferred that j has a value of 1 to 250, it is preferred that k has a value of from greater than zero to 20 and it is highly preferred that k has a value of from 1 to 15, it is preferred that l has a value of 1 to 100 and it is highly preferred that I has a value of 1 to 50, it is preferred that m has a value of 1 to 500 and it is highly preferred that m has a value of 1 to 250, it is preferred that n has a value of from greater than zero to 20 and it is highly preferred that n has a value of from greater than 1 to 15, it is preferred that p has a value of 1 to 100 and it is highly preferred that p has a value of 1 to 50, it is preferred that q has a value of 2 to 6, it is preferred that r has a value of 1 to 2500 and it is highly preferred that r has a value of 20 to 1000, it is preferred that s has a value of 2 to 6, it is preferred that t has a value of 2 to 4, it is preferred that u has a value of from 1 to 100 and it is highly preferred that u has a value of 5 to 50, it is preferred that v has a value of from 1 to 100 and it is highly preferred that v has a value of 5 to 50, it is preferred that w has a value of from 1 to 100 and it is highly preferred that w has a value of 1 to 50. It is preferred that the cross-linked polydiorganosiloxane polymer of component (III) is triorganosiloxy endblocked at each terminal of the polymer, and it is highly preferred that the polymer is trimethylsiloxy endblocked at each terminal of the cross-linked polymer.
The method used to prepare the crosslinked polydiorganosiloxane polymers is disclosed in European Patent Application No. 0663225. A specific example of the method for producing the crosslinked polydiorganosiloxane polymers will now be described. Preparation of a crosslinked polydiorganosiloxane polymer was done through the following steps: (I) a charging step in which a linear polysiloxane having hydrogen atoms in its side chains, a polysiloxane having vinyl groups and a catalyst for promoting the reaction, particularly platinum catalysts such as an isopropanol solution of H2PtCl66H2O with a 2% methanol solution of sodium acetate are put in a reactor, (II) an agitation/heating step in which agitation is conducted, for example, at 40xc2x0 C. for 30 minutes, (III) an input step in which a polyoxyalkylene and a solvent (isopropanol) are put in the reactor, (IV) a reflux step in which the isopropanol is refluxed, for example, at 80xc2x0 C. for 1.5 to 2 hours while monitoring the reaction rate of Sixe2x80x94H, (V) a stripping step in which the isopropanol is stripped, for example, at 130xc2x0 C. under a reduced pressure of 25 mmHg, and (VI) a final step in which the reduced pressure condition of step (V) is released and the reaction mixture is cooled to 60xc2x0 C. to obtain a final product.
An example of a linear polysiloxane having hydrogen atoms in its side chains suitable for step (I) is a polysiloxane having its formula selected from: 
wherein Me hereinafter denotes methyl and j, k, l, m, n, and p are as defined above. An example of a polysiloxane having vinyl groups suitable for step (I) is a polysiloxane having the formula: 
wherein Me denotes methyl, Vi hereinafter denotes vinyl, and r is as defined above. The reaction of these two compounds in step (II) results in a cross-linked siloxane polymer having the formula 
Introduction of a polyoxyalkylene group into the obtained crosslinked organopolysiloxane polymer (steps III-VI) is accomplished by reacting the crosslinked polymer with a polyoxyalkylene compound having its formula selected from the group consisting of 
wherein u, v, and w are as defined above.
Preferred as Component (III) are cross-linked polydiorganosiloxane polymers having the formula 
wherein Me denotes methyl, j has a value of 1 to 250, k has a value of from 1 to 15, l has a value of 1 to 50, m has a value of 1 to 250, n has a value of from greater than 1 to 15, p has a value of 1 to 50, r has a value of 20 to 1000, u has a value of 5 to 50, v has a value of 5 to 50, and R15 is hydrogen, methyl, or C(O)CH3.
Component (III) is present in the silicone foam control compositions of this invention in an amount from 1-50 weight parts, preferably from 5 to 20 weight parts, and most preferably from 10 to 20 weight parts, said weight parts being based on the total weight of the composition.
Component (IV) is at least one finely divided filler. The finely divided filler is exemplified by fumed, precipitated, or plasmatic TiO2, Al2O3, Al2O3/SiO2, ZrO2/SiO2, and SiO2. The finely divided filler can be hydrophilic or hydrophobic. The filler can be hydrophobed during manufacture (i.e. in-situ) or independently. Various grades of silica having a particle size of several millimicrons to several microns and a specific surface area of about 50 to 1000 m2/g, preferably a surface area of 50 to 300 m2/g, are commercially available and suitable for use as component (iv). Preferably component (IV) is a hydrophobic silica having a surface area of about 50 to 300 m2/g. Hydrophobic precipitated silicas are especially preferred as component (IV).
Component (IV) is present in the silicone foam control compositions of this invention in an amount from 1-20 weight parts, preferably from 1 to 10 weight parts, and most preferably from 2 to 6 weight parts, said weight parts being based on the total weight of the composition.
The silicone foam control compositions of this invention can further comprise (V) a polyglycol. The polyglycol is exemplified by polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymers, condensates of polyethylene glycol with polyols, condensates of polypropylene glycol with polyols, and condensates of polyethylene glycol-polypropylene glycol copolymers with polyols.
Component (V), if used, is present in the silicone foam control compositions of this invention in an amount from 1-50 weight parts, preferably from 5 to 20 weight parts, and most preferably from 10 to 20 weight parts, said weight parts being based on the total weight of the composition.
In addition to the above-mentioned components, the silicone foam control compositions of the present invention may also contain adjuvants such as corrosion inhibitors and dyes. The compositions of the present invention may be prepared by blending components (I)-(IV), and any optional components, to form a homogenous mixture. This may be accomplished by any convenient mixing method known in the art such as a spatula, mechanical stirrers, in-line mixing systems containing baffles, blades, or any of the like mixing surfaces including powered in-line mixers or homogenizers, a drum roller, a three-roll mill, a sigma blade mixer, a bread dough mixer, and a two roll mill. The order of mixing is not considered critical.
The present invention also relates to a process for controlling foam in a foaming system wherein the above-described silicone foam control composition is added to a foaming or foam-producing system, in an amount sufficient to reduce foaming, as determined by routine experimentation. Typically, the silicone foam control compositions of the present invention are added at a concentration of about 0.001 to 0.1 weight parts based on the weight of the foaming system, however the skilled artisan will readily determine optimum concentrations after a few routine experiments. The method of addition is not critical, and the composition may be metered in or added by any of the techniques known in the art. Examples of foaming systems contemplated herein include media encountered in the production of phosphoric acid and in sulphite or sulphate process pulping operations, bauxite digestion medium in the production of aluminum, metal working fluids, paper manufacture, detergent systems, hydrocarbon based systems, etc. The compositions of the present invention can be used as any kind of foam control composition, i.e. as defoaming compositions and/or antifoaming compositions. Defoaming compositions are generally considered as foam reducers whereas antifoaming compositions are generally considered as foam preventors. The compositions of this invention find utility as foam control compositions in various media such as inks, coatings, paints, detergents, pulp and paper manufacture, textile dyes, textile scours, and hydrocarbon containing fluids.